Rotor tilt

ABSTRACT

A system for controlling the tilt of a rotor on a gyro includes a sensing device on the rotor housing for detecting tilt, together with light generating devices mounted on opposite sides of the rotor housing and responsive to the tilt detecting device. Light sensors are mounted on the gyro housing and are responsive to light from the light generating devices on the rotor housing. The light detecting devices provide a control signal to a torqueing motor to apply a corrective force to the gyro system. The torque motor is continuously operated, and will rotate in a first direction until a signal is received from at least one of the light sensing devices, whereupon the direction of rotation reverses until light is not detected by one of the sensors. Use of light activated control system to transmit the error signal obviates the use of any friction-producing physical attachment with the components of the gyro in order to transmit such error signal to the torque motor control system.

United States Patent [45] Nov. 28, 1972 Thomas W. Stell, Fort Bend, bothof Tex.

Assignee: Sperry-Sun Well Surveying Company, Sugar Land, Tex.

Filed: May 18, 1970 Appl. No.: 38,263

Primary Examiner Manuel A. Antonalras Attamey-George L. Church, DonaldR. Johnson, Wilmer E. McCorquodale, Jr. and John E. Holder ABSTRACT Asystem for controlling the tilt of a rotor on a gyro includes a sensingdevice on the rotor housing for detecting tilt, together with lightgenerating devices mounted on opposite sides of the rotor housing andresponsive to the tilt detecting device. Light sensors are mounted onthe gyro housing and are responsive to light from the light generatingdevices on the rotor housing. The light detecting devices provide acontrol signal to a torqueing motor to apply a corrective force to thegyro system. The torque motor is continuously operated, and will rotatein a first direction until a signal is received from at least one of thelight sensing devices, whereupon the direction of rotation reversesuntil light is not detected by one of the sensors. Use of lightactivated control system to transmit the error signal obviates the useof any friction-producing physical attachment with the components of thegyro in order to transmit such error signal to the torque motor controlsystem.

7 Clains, 3 Drawing Figures [52] US. Cl. ..74/5.45, 74/5.47, 74/5.6 [51]Int. Cl. ..G01c 19/30 [58] Field of Search ..74/5.6, 5.41, 5.45, 5.47

[56] References Cited UNITED STATES PATENTS 2,423,270 7/1947 Summers, Jr..74/5.45 2,505,021 4/ i950 Weems et al. ..74/5.45 X 2,828,629 4/1958Summers, Jr. ..74/5.45 3,409,350 11/1968 Call ..74/5.45 X 3,424,5231/1969 Branigan ..74/5.45 X

PATENTEDNIIV23 I n. 3. 703.832

sum 1 or 2 F'IG I INVENTORS JAMES M. LINDSEY OMAS w. STELL ATTORNEYPATENTED 3. 703, 832

' SHEET 2 [If 2 5! K IDETI [DETI DETI IIDETI AMP S JPTE 64 FIG. 2INVERTER INVENTORS F IG. 3

JAMES M. LINDSEY THOMAS W. STELL ATTORNEY ROTOR TILT BACKGROUND OF THEINVENTION This invention relates to a gyro control, and moreparticularly, to a system for maintaining the rotor of a gyro in apredetermined attitude. In a typical gyro control system, some sort ofphysical attachment is used to detect gyro tilt and transmit theindication of such tilt to a restoring device. A torque motor isnormally used to apply a torqueing force to the vertical axis of thegyro in order to correct tilt of the inner gimbal or rotary housing.Although slip rings and the like, which have been used in the past forsuch purposes, minimize the amount of external torque or force upon thegyro components, slip rings or any other type of physical attachment tothe vertical or horizontal components of a gyro are undesirable becausethey do cause friction to some degree, which creates drift and tilt inthe gyro. It is therefore desirable to find a frictionless means oftransferring an indication of tilt from these components to a controlfunction or in the present case, a torque motor. The torque motor thenexerts the necessary force on the vertical axis of the gyro to maintainthe rotor axis in some desired positional relationship.

It is therefore an object of the present invention to provide a new andimproved gyro control system.

SUMMARY OF THE INVENTION With this and other objects in view, thepresent invention contemplates a gyro control system responsive to atilt indicating device. A level detector on a gyro component develops acontrol signal for activating a light source on the gyro component.Light detectors on an inactive portion of the gyro housing sense lightfrom the source to send a control signal to a torqueing motor. Thetorque motor drives a device for applying a restoring force to a gyrocomponent.

A complete understanding of this invention may be had by reference tothe following detailed description, when read in conjunction with theaccompanying drawings illustrating embodiments thereof.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial cross-sectionalview of a wellbore instrument embodying a gyro control system inaccordance with the present invention;

FIG. 2 is a schematic circuit diagram of electronic circuitry forproviding control to a torqueing motor; and

FIG. 3 is an alternative arrangement of an apparatus for transmitting atorqueing force from the motor to a component of the gyro system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. 1 ofthe drawings, a wellbore tool 11 is shown having a housing 12 forencasing a gyro instrument. A photographic recording apparatus or thelike may be mounted in a section 13 above the gyro for making readingsindicative of the gyro position. Alternatively, circuitry may beprovided for transmitting a signal to the surface via a cable, whichsignal may be utilized to provide an instantaneous recording or read-outrepresenting the gyro position. Below the instrument section is anelectrical section 16 including a power supply and circuitry forcontrolling the operation of the torqueing motor 17. The outer gimbal 19of the gyro has upwardly and downwardly extending vertical shafts 21, 22respectively, which in turn are supported by bearings for rotationwithin the instrument housing. At the lower end of the lower verticalshaft 22, a cup 23 is provided within the housing for receiving thelower end of the shaft and the bottom of the cup to furnish a pivotalsupport for the shaft. Annular bearings (not shown) are provided betweenthe shaft 22 and a horizontal partition 26 within the housing forsupport in a horizontal direction. The cup 23 is filled with mercury orsome such conducting fluid 27, so that an electrical current applied tothe bottom of the cup is transmitted by means of the conducting fluid tothe vertical shaft 22 of the gyro. At the upper end of the gyro, theupwardly extending vertical shaft 21 likewise has a mercury filled cup28, mounted thereon. A wiper wire 29 extends inwardly from the wall ofthe housing 12, and is bent to extend downwardly into the mercury filledcup 28 to form a second conducting path to the gyro. The upper shaft 21is supported in a horizontal direction by annular bearings 31. Aninstrument face 32 may be connected to the upper end of the cup or shaftto provide indications of the gyro position. Photographic apparatus insection 13 is used to record the position of the instrument face. Thevertical shafts 21, 22 are in electrical communication with the outergimbal of the gyro. Insulating members 33 are positioned in the gimbalwalls so that the gimbal is divided into two separate conducting paths.These conducting paths in turn are in communication with opposedhorizontal shafts 34,36 which are received within opposed walls of theouter gimbal and which extend inwardly to support an inner gimbal 37 ofthe gyro. The inner gimbal of the gyro is pivotally mounted on suchhorizontal shafts 34, 36 and supports a rotor (not shown) within a rotorhousing 38. The rotor is mounted about another horizontal shaft 39perpendicular to the shafts 34, 36 of the inner gimbal. As is well knownin the construction of such gyro instruments, the inner gimbal 37 isdivided into separate insulated portions similarly to the outer gimbal,which portions provide separate conducting paths from the shafts 34, 36to the rotor for supplying power to the rotor.

A level detecting switch 42 is mounted on the bottom side of the innergimbal 37 parallel with the rotor shaft 39. Light sources such as smallneon lamps 46 are mounted on the bottom side of the inner gimbal 37 andon opposite sides thereof perpendicular to the rotor shaft 39.Electrical power which is used to drive the rotor motor is also used tooperate the neon lamps 46 in series with the switch 42. Light'detectors51, which may be in the form of photocells or other light sensitivedevices, are positioned at spaced locations about the periphery of thetool housing below the outer gimbal 19. In the embodiment of theapparatus shown in FIG. 1, the light detectors are placed at fourequidistant locations about the inner wall of the housing in thehorizontal partition 26.

As has been described with respect to the Background of the Invention,it is-desirable to maintain the rotor housing of a gyro in either a truehorizontal position relative to earth, or in some fixed position withrespect to the vertical or outer gimbal. It is first necessary to detectany changes in the attitude of the inner gimbal with respect to suchfixed or desired position in order to make corrections, through atorqueing motor system, for such changes. The torque motor 17 is mountedwithin the housing 12 below the horizontal partition 26. A ball bearing52 is provided in the partition to support an output shaft 53 on themotor 17. A

grooved wheel 54 is mounted on the upper end of shaft 53. A rubber orotherwise pliant ring member 56 is positioned in the groove in the wheel54. A cup-shaped element 57 is provided on the lower surface of theouter gimbal 19 and serves as a friction receiving member. The element57 has a vertical surface 58 which is arranged in close proximity withthe outer peripheral surface of the grooved wheel 54. The ring member 56is normally not in contact with the surface 58 unless the wheel 54 isrotating, which in accordance with the operation of the apparatus isconstantly occurrmg.

Referring next to FIG. 3 of the drawings, an altemative arrangement ofthe corrective force transmitting device is shown. The torque motor 17is shown mounted within the housing 12. An output shaft 71 extendsthrough horizontal member 26 and is supported therein by means ofbearing 72. A rubber wheel 73 is positioned on the shaft. The verticalaxis 22 of the outer gimbal is likewise mounted for rotation within themember 26. A bearing 74 is mounted on the shaft 22 and is arranged sothat its outer peripheral surface 77 is contacted by a mating peripheralsurface 76 on the rubber wheel 73. Of course a gear arrangement may beemployed to transmit the movement of the wheel to the bearing byproviding compatible gear teeth on the respective surfaces 77 and 76.

Referring next to FIG. 2 of the drawings, the electrical circuitryportion of the system, which is mounted in section 16 of the toolhousing is shown in conjunction with the light sensitive devices 51. Thelight sensitive devices 51 are shown connected in parallel with anamplifier 61. The amplifier signal feeds a loop 62 including a solidstate double pole double throw switch 63 in a bridge configuration andhaving an inverter 64 connected to one of its input lines. The output ofthe switch is connected to a reversible motor 66.

The electrical circuitry section 16 of the housing includes a powersupply for driving the gyro rotor. The power supply signal is applied tothe rotor in the manner described above by means of separate insulatedsections of the gimbal housing for providing current paths. Since thepower signal is available to the rotor, the signal is easily furnishedto the level switch and neon lamps mounted on the rotor housing. Theneon lamps are connected in series with the level switch.

Although the system will be described herein as maintaining the rotor ina true horizontal position, it is readily seen that the rotor could bemaintained in any desirable position with a tilt detector or the likebeing determinative of the movement of such rotor housing from thatdesired position. The level detector 42, which is mounted on the rotorcan be any of a number of devices having the capability of detectingtilt, and may be either of a variable impedance configuration, or astraight on-off type switch of the single pole, single throwconfiguration such as a simple mercury switch.

In the operation of the apparatus described above, while the gyro isoperating, forces are acting upon its components which tend to cause aprecessing moment, which in turn causes the rotor housing 38 to tiltabout its axes 34, 36. It is desirable for reasons described above tomaintain such rotor housing in a constant plane, whether it be a planehorizontal to the earths surface or one perpendicular to the verticalaxis of the borehole tool. In any event, a level switch 42 mounted onthe rotor housing is arranged so that when it tilts from itspredetermined plane, contact is made within the switch which completesan electrical circuit. The circuit path, which is completed by theswitch includes a pair of neon lamps 46, which are mounted on oppositesides of the lower side of the rotor housing. Activation of these lampscauses light emanating therefrom to be detected by the light detectingdevices 51 mounted about the periphery of the interior bore of thehousing 12 below the gyro. These light detectors, which in the presentconfiguration number four, and are evenly spaced about the housing, areconnected in parallel so that a light detected by any one of thedetectors causes a signal to be applied (FIG. 2) to the amplifier 61 inthe control circuit. This amplifier in turn provides an output signalwhich is applied to both sides of a loop circuit 62. An inverter 64 inthe circuit causes a signal of opposite polarity to be applied to oneside of a double pole double throw switch than is appliedto the otherside. The solid state switch 63 thus produces a signal to the motor. 66for driving the motor in a first direction. The motor will in turn drivein this direction and causes the wheel on its output shaft to engage thefriction receiving member connected to the vertical shaft of the gyro.Rotation of the wheel causes the rubber ring positioned within a groovetherein to expand outwardly into contact with the inner surface of thefriction receiving means thereby applying a fric-- tional force to suchsurface. This force is transmitted through the vertical axis of the gyroto the gyro mechanism causing a precessing moment in the mechanism whichtends to move the gyro rotor housing. The housing which has alreadyvbeen tilted by some forces acting thereon will now tend to move in anopposite direction until it has become leveled, at which time the switch42 will break its contact which in turn causes the lamps to beinactivated wherein no light is detected by the detectors 51.Thereafter, the output of the amplifier is zero, which is opposite tothe output seen by one side of the double pole double throw switch sothat the switch is operated in an opposite mode causing a reversepolarity of power applied to the motor, which causes the motor toreverse. Reversal of the motor then in turn as described above, appliesa frictional force to the gyro parts in an opposite direction causingthe rotor housing to precess whereupon the level switch will againdetect an untilted condition, again reversing the motor direction. Thisconstant reversal of the motor and precessing force applied to the gyroapparatus with the consequent reverse tilting of the rotor housing takesplace constantly in accordance with the arrangement described above. Ofcourse, it is seen that various arrangements of the electrical circuitrywill permit other operations of the corrective force applying motor.

When the torque motor is moved in first one direction and then another,its grooved wheel is likewise rotated therewith, whereupon the belt orrubber ring member is extended outwardly slightly due to centrifugalforce into contact with the inner vertical surface of the frictionreceiving member connected to the vertical gimbal of the gyro. The useof the belt or rubber member as a torque transmitting means provides avery inefficient transmission means so that only a slight amount of thework provided by the rotating wheel is transmitted to the frictionreceiving member. Thus the slight frictional force which is transmittedis adequate to provide sufficient restorative precessing force to thegyro apparatus.

In the alternative embodiment shown in FIG. 3, the restoring forcesupplied by the torque motor is transmitted to a rubber wheel having itsouter peripheral surface 77 in constant contact with the mating surface76 of the bearing 74 positioned on the vertical shaft of the gyro. Thuswhen the torque motor "is operated, the bearing is rotated about theshaft 22 with the slight friction generated between the balls of thebearing and the shaft providing the slight restorative force necessaryfor precessing the gyro. It is noted that because the force of the ballbearings is applied to the outer diameter of the shaft 22 the moment armof the force, that is, the radius of the shaft, is much less than in theembodiment of FIG. 1 and therefore, the friction generated between theball bearings and the axis 22 is of less moment than that applied to thefriction receiving member of FIG. 1.

While a particular embodiment of the present invention has been shownand described, it is apparent that changes and modifications may be madewithout departing from this invention in its broader aspects, andtherefore, the aim in the appended claims is to cover all such changesand modifications as fall within the true spirit and scope of thisinvention.

What is claimed is:

1. In a gyroscope apparatus, means for applying corrective forces to theapparatus, which means comprises: means for detecting a misalignment inthe relative positions of the gyro parts; motive means operative inresponse to said detecting means; and means responsive to the operationof said motive means for applying a frictional force to a portion ofsaid apparatus, said friction applying means being engageable with saidportion only upon operation of said motive means.

2. The apparatus of claim 1 wherein said portion of said apparatusincludes a member extending outwardly of the axis of said portion andhaving a surface extending in a direction parallel with the axis, withsaid friction applying means including a rotatable member which is movedfrom its normal non-engaged position into an engaged position with saidsurface due to a centrifugal force generated by the operation of saidmotive means.

3. The apparatus of claim 2 wherein said motive means includes a motorand shaft, with said friction applying means including a grooved membermounted on said shaft and a pliant ring shaped member received in thegroove on said member so that said ring shaped member is in a planeperpendicular to the motor shaft and said axis.

4. In a gyroscope apparatus, means for applying corrective forces to theapparatus which means comprises: means for detecting a mis-alignment inthe relative position of the gyro parts; a shaft connected to one of thegyro parts; a bearing rotatably mounted on said shaft; motive meansoperable in response to said detecting means; and means for transmittinga force from said motive means to said bearing.

5. The apparatus of claim 4 wherein the gyroscope apparatus includes anouter gimbal having a vertical axis, wherein said bearing is mounted onsaid vertical axis, said motive means is a reversible motor having anoutput shaft parallel to said vertical axis, and said transmitting meansis a member on said shaft engagable with the outer peripheral surface ofsaid bearing.

6. In a gyroscope apparatus having a rotor, rotor housing and verticalgimbal, means for controlling the tilt of the rotor housing, which meanscomprises: means on the apparatus for detecting rotor housing movementfrom a predetermined position; means operatively connected to thevertical gimbal for receiving restoring forces; means supporting a ringmember for selective engagement with said force receiving means; andmeans responsive to said detecting means for rotating said supportingmeans whereby said ring member is moved by centrifugal force intocontact with said force receiving means.

7. In a gyroscope apparatus having a rotor, rotor housing, and verticalgimbal positioned within a gyro housing, means for controlling the tiltof the rotor housing, which means comprises: selectively operable energyemanating means on the rotor housing; rotor housing tilt detection meansfor operating said energy emanating means; means on the gyro apparatusfor detecting emanated energy; and means responsive to such detectedenergy for applying a restorative force to the gyroscope apparatus, saidmeans for applying a restorative force including, motive means operablein response to such detected energy, and means responsive to theoperation of said motive means for applying a frictional force to aportion of said apparatus, said frictional applying means beingengageable with said portion only upon operation of said motive means.

1. In a gyroscope apparatus, means for applying corrective forces to theapparatus, which means comprises: means for detecting a misalignment inthe relative positions of the gyro parts; motive means operative inresponse to said detecting means; and means responsive to the operationof said motive means for applying a frictional force to a portion ofsaid apparatus, said friction applying means being engageable with saidportion only upon operation of said motive means.
 2. The apparatus ofclaim 1 wherein said portion of said apparatus includes a memberextending outwardly of the axis of said portion and having a surfaceextending in a direction parallel with the axis, with said frictionapplying means including a rotatable member which is moved from itsnormal non-engaged position into an engaged position with said surfacedue to a centrifugal force generated by the operation of said motivemeans.
 3. The apparatus of claim 2 wherein said motive means includes amotor and shaft, with said friction applying means including a groovedmember mounted on said shaft and a pliant ring shaped member received inthe groove on said member so that said ring shaped member is in a planeperpendicular to the motor shaft and said axis.
 4. In a gyroscopeapparatus, means for applying corrective forces to the apparatus whichmeans comprises: means for detecting a mis-alignment in the relativeposition of the gyro parts; a shaft connected to one of the gyro parts;a bearing rotatably mounted on said shaft; motive means operable inresponse to said detecting means; and means for transmitting a forcefrom said motive means to said bearing.
 5. The apparatus of claim 4wherein the gyroscope apparatus includes an outer gimbal having avertical axis, wherein said bearing is mounted on said vertical axis,said motive means is a reversible motor having an output shaft parallelto said vertical axis, and said transmitting means is a member on saidshaft engagable with the outer peripheral surface of said bearing.
 6. Ina gyroscope apparatus having a rotor, rotor housing and vertical gimbal,means for controlling the tilt of the rotor housing, which meanscomprises: means on the apparatus for detecting rotor housing movementfrom a predetermined position; means operatively connected to thevertical gimbal for receiving restoring forces; means supporting a ringmember for selective engagement with said force receiving means; andmeans responsive to said detecting means for rotating said supportingmeans whereby said ring member is moved by centrifugal force intocontact with said force receiving means.
 7. In a gyroscope apparatushaving a rotor, rotor housing, and vertical gimbal positioned within agyro housing, means for controlling the tilt of the rotor housing, whichmeans comprises: selectively operable energy emanating means on therotor housing; rotor housing tilt detection means for operating saidenergy emanating means; means on the gyro apparatus for detectingemanated energy; aNd means responsive to such detected energy forapplying a restorative force to the gyroscope apparatus, said means forapplying a restorative force including, motive means operable inresponse to such detected energy, and means responsive to the operationof said motive means for applying a frictional force to a portion ofsaid apparatus, said frictional applying means being engageable withsaid portion only upon operation of said motive means.